Cyclic voltammetry experiments were performed using a CHI-1040C electrochemical workstation (CH Instrument) in the three-electrode system. A gold disc electrode (Au; ϕ = 1.6 mm, BAS Instruments) was used as the working electrode, a Ag/AgCl/3 M KCl as the reference electrode and a gold wire served as the auxiliary electrode. Before each measurement the surface of the working electrode was polished with 1 μm Al2O3 powder on a wet pad. After each polishing, the electrode surface was rinsed with direct stream of ultrapure water to completely remove alumina from the electrode surface, and dried with argon. Next, the gold electrodes were electrochemically cleaned by cycling them in 0.1 M H2SO4 solution in a potential range from −0.3 to 1.5 V (vs. Ag/AgCl/3 M KCl) with scan rate 0.05 V s−1, until a stable voltammogram typical for a bare gold electrode was obtained.
The double-layer capacitance measurements for bare and SAMs coated gold electrodes were performed in 0.1 M deoxygenated phosphate buffer (PB) of pH 7.0 containing 150 mM K2SO4 in the potential range from −0.1 to 0.5 V (vs. Ag/AgCl/3 M KCl) at scan rate 1 V s−1.
The double-layer capacitance measurements for bare and SAMs coated gold electrodes were performed in 0.1 M deoxygenated phosphate buffer (PB) of pH 7.0 containing 150 mM K2SO4 in the potential range from −0.1 to 0.5 V (vs. Ag/AgCl/3 M KCl) at scan rate 1 V s−1.